Leishmania species are protozoan parasites that cause important human diseases in the tropics and subtropics worldwide and, thus, represent a major public health problem. Ether lipids are important constituents of Leishmania membranes, and more importantly, are structural components of various virulence factors, such as the very abundant cell surface lipophosphoglycan and the glycosylphosphatidylinositol(GPI)-anchored protease GP63. Both play crucial roles during the entire life cycle of the parasite. Ether lipid-based drugs such as miltefosine, currently used in clinical trials, inhibit parasite growth in vitr and in vivo, and are likely to interfere with the ether lipid biosynthetic pathway. This supports te idea that this metabolic route can be targeted for further drug design. Our previous studies have established that the first two enzymes of the ether lipid biosynthetic pathway in L. major, dihydroxyacetonephosphate acyltransferase LmDAT and alkyl dihydroxyacetonephosphate synthase LmADS, are implicated in the synthesis of the virulence factor lipophosphoglycan and cellular ether lipids, which play a crucial role in parasite pathogenesis. Our preliminary results have suggested that i) LmFAR is involved in the production of fatty alcohols which are essential for the synthesis of ether lipids, and ii) LmFAR is important for growth of the parasite. This proposal will test the central hypothesis that Leishmania peroxisomal fatty acyl-CoA reductase LmFAR is essential for ether lipid metabolism and generation of the virulence factor lipophosphoglycan, and consequently, for pathogenesis. To test this hypothesis, we propose to use two Specific Aims that combine a multidisciplinary approach that involves molecular biology, genetics, biochemistry, and cell biology techniques. In Specific Aim 1, we will investigate the enzymatic properties of LmFAR and its subcellular localization. In Specific Aim 2, we will assess the importance of LmFAR in ether lipid biosynthesis, virulence, and sensitivity to ether lipid-based drugs. Understanding the function of LmFAR is important for the development of novel strategies to prevent and treat Leishmania infections. In addition, this project will enhance the research environment at St. John's University by providing underprivileged students with numerous opportunities to learn the fundamentals of biomedical research.